Method of making rock drill bits



March 8, 1949. J, c, -n5 2,463,953

H G ROCK DRILL BIT Filed Jan. 14, 1947 s Sheets-Sheet 1 March 8, 1949. J, c, cum-ls 2,463,953

METHOD OF MAKING ROCK DRILL BITS Filed Jan. 14, 1947 3 Sheets-Sheet 2 LII Jbiwzdu Add-Mam awg.

March 8, 1949.- J. c. CURTIS 2,463,953

METHOD OF MAKING ROCK DRILL BITS Filed Jan. 14, 1947 3 Sheets-Sheet 3 I W h I 1520671107.- f07znU. Uurtzk.

Patented Mar. 8, 1949 Mn'rnon OF MAKING noon DRILL BITS John 0. Curtis, Claremont, N. H., assignor to Joy Manufacturing Company, a corporation of Pennsylvania Application January 14, 1947, Serial No. 122,044

1 17 Claims. This invention relates to methods of forming rock drill bits. Efforts have heretofore been made to construct rock drill bits from specially rolled bar stock instead of from individual forgings. According to such prior methods there has first been rolled a section of bar stock in such a manner as to provide lobes of a length suflicient to permit the manufacture therefrom of the cutting ends of two bits, and with the lobes spaced longitudinally from each other distances equal to slightly more than twice the length of the portion of each bit which is used to effect the mounting thereof on a drill steel. The bar is cut into sections by cuts made midway between adjacent lobes to provide units of two bits connected together face to face. These units are then drilled at their opposite ends, making it necessary that the units be turned end for end during the process of drilling. The unitsare then cut apart midway between the ends of the lobes to provide two bits, each of which is then milled at its face to provide the proper cutting edges. This results in little advantage over present methods of bit manufacture from forgings, aside from the use of bars as the original stock from which the bits are made.

According to my improved methods the bar stock may be rolled for the construction of bits having skirt portions suitably internally formed for attachment to the ends of drill steels, or the bar stock may be rolled to a form which will be adapted for the manufacture of bits having suitably formed shanks adapted to be received in sockets carried at the ends of drill steels. Irrespective of which bit form is to be ultimately produced, the bar stock is rolled to provide lobes of the proper shape and length for single bits only, and these lobes are spaced apart distances only substantially equal to the length desired for the portion of each bit which is to be used to effect its mounting upon a drill steel. Then each bit is desirably drilled, threaded internally or externally, or otherwise formed for interlocking attachment to a drill steel, shaped; and then, and then only, cut off of thebar by an automatic machine; and no handling of bit blanks is necessary during these operations, which are performed on the bar as received in suitably formed shape. Thereafter the ends of the lobes are suitably machined to form the cutting faces of the bits.

An object of the present invention is to provide an improved method of making rock drill bits or the like. Another object is to provide an improved method of forming rock drill bits whereby the cost of manufacture issubstantially reduced 2. and. more nearly perfect bits may be assured. A further object of my invention is to provide an improved method of making rock drill bits adapted to be fixed by their skirt portions to drill steels. Still another object of my invention is to provide an improved method of forming rock drill bits adapted to be connected by their shanks to drill steels. Other objects of this invention and advantages thereof will hereinafter more fully appear.

In the drawings, in which two illustrative methods of practicing my invention in its broader aspects are shown for purposes of illustration- Fig. l is a side elevational view of a section of roller bar stock from which a rock drill bit is to be formed in accordance with the first illustrative practice of my invention.

Fig. 2 is a view in longitudinal section through and end portion of the bar shown in Fig. 1, illustrating a step in the formation of the drill bit in accordance with the practice of the improved method illustrated in Figs. 1 to 9.

Figs. 3, 4, 5,6 and '7 are views similar to Fig. 2, showing other steps in the improved method.

Fig. '8 is a view, partially in side elevation and partially in longitudinal section, of a completed drill bit adapted to be secured by means of its skirt to a drill steel. I

Fig. 9 is an end elevational view of the drill bit shown in Fig. 8, looking toward the cutting face.

Fig. 10 is a side elevational view of a section of rolled bar stock from which a rock drill bit adapted to be attached by its shank to a drill steel is to be formed in accordance with another practice of my improved method. 4

Fig. 11 is a view in longitudinal section through an end portion of the bar shown in Fig. 10, illustrating the simultaneous performance of two operations in the formation of the drill bit, in accordance with the practice of the improved method illustrated in Figs. 10 to 13.

Figs. 12 and 13 are views similar to Figs. 6 and 7, showing other steps of the practice of the improved method of Figs. 10 to 13.

Fig. 14 is a view in longitudinal section, of a completed drill bit of a type held by its shank to a drill steel.

Fig. 15 is an end elevational view of the bit shown in Fig. 14, looking toward the cutting face.

In accordance with the improved method of forming a rock drill bit utilizing the interior surfaces of the skirt to connect it to a drill steel, .which improved method is illustrated in Figs. 1 to '7, an elongated section of metal or bar stock B is first preformed by causing the heated metal means or stock to flow into proper shape in any suits-1e manner, as by rolling, with appropriately located lobes I of special formation spaced by cylindrical bar sections 2 of a length approximately equal to the sleeve or skirt portions of finished bits. The preforming or rolling step need not be illustrated, but it will be so performed as to provide, united in the form of a continuous bar, a scrim of winged bodies with round prospective skirt or attachment portions, the wings of the body portions conforming, except for the excess stock necessary to insure adequate size in the finished bit relatively closely, preferably, to the wing shape of a finished bit, and the connecting portions being also of approximately the desired finished outside diameter. The rolling is such that the blanks all point the same way. The rolled bar stock section in its completed form, as shown in Fig. 1, is first placed in the chuck of a conventional automatic rotary machine, such as an automatic lathe, in such a position that the butt ends of the successive bit blank portions will be presented to the tools, and when suitably secured in position an end of the rolled section, first cut if necessary to present the end of a prospective skirt portion 2, is centrally drilled at 3 by a con- 4 ventional driIlbit 4 (Fig. 2). The drilled hole 3 is then enlarged by a conventional drill 5 (Fig. 3), desirably a four-lip drill, to provide an enlarged central bore 6 of a size suitable for tapping. As shown in Fig. 4, a central hole 1 is then formed by a conventional drill 8, to provide in the finished bit the cleansing fluid passage, and, desirably concurrently, the bit body periphery (the wings) is turned at 9 by a conventional turning tool In to give the bit the desired gauge, and the end of the body section is faced at II by a conventional facing tool I2. Thereafter, as shown in Fig. 5, the wings are beveled at I3 by a conventional beveling tool Hi to locate the chopping edges of the finished bit in the desired position. The enlarged bore 6, as shown in Fig. 6, is then threaded at I5 by a conventional tap l6 and then the bit is cut oil at I! (Fig. 7) by a conventional cutting-01f tool i8. The operations of drilling, turning, facing, beveling, tapping and cutting off are repeated in sequence on successive blank portions while these still remain on the bar, thereby'to separate the section of rolled bar stock into a number of separate bit blanks only when all of the operations which can be performed on an automatic machine have been completed. The bit blanks as shown, in the process of being cut off, in Fig. 7, are milled in a conventional milling machine to form a central recess 49 and to provide an opening for the bore 7 through the forward end of the bit. These blanks are further milled transversely to provide diametric cutting edges 20 and arcuate peripheral chopping edges 2|. The completed bit may assume a form similar to that disclosed in a patent to P. H. Nast, No. 2,168,102, granted Aug. 1, 1939.

The earlier method steps performed in the formation of each bit, as above outlined, are, as previously stated,accomplished by an automatic machine, and while the ultimate bit is still integral with the bar, and the steps of drilling. turning, facing, beveling, tapping and cutting oil may be caused to take place automatically, without manual intervention. The milling of the cutting face is performed subsequently to the cutting up of the rolled bar stock section into a series of separate bit blanks and after the bit blanks have been discharged from the automatic machine, the

bit blanks being placed in operative position on a milling machine where the blanks are milled into final shape. It will of course be understood that the number of operations may be varied, and their sequence varied also, if desired. For example, the first' and third drilling operations u might be performed in a relatively continuous operation.

After all of the machining operations are completed, the bit will be hardened, drawnandp quenched or otherwise heat treated as may be necessary.

Turning next to the method of forming drill bits connectible by their shanks to drill steels, which method is shown in its illustrative practice in Figs. 10 to 13, it will be observed that an elongated section of metal or bar stock B is first preformed by causing the heated metal or stock to flow into a proper shape in any suitable manner, as by rolling, with appropriately located lobes I of special formation spaced by cylindrical bar sections 2' of a length approximately equal to the shank portions of finished bits. The preforming or rolling step need not be illustrated, but

. it will be so preformed as to provide, united in the form of a continuous bar, a series of winged butts with round prospective shank portions, the wings of the body portions conforming, for

the excess stock necessary to insure adequate size in the finished bit, relatively closely, preferably, to the wing shape of a finished bit, and the connecting portions being also of not much greater size than the desired finished outside diameter. The rolling is suchthat the blanks all point in the same direction. The rolled bar stock section in its completed form, as shown in Fig. 10, is first placed in the chuck of a conventional automatic rotary machine, such as an automatic lathe, in such a position that the butt 0 ends of the successive bit blank portions will be presented to the tools, and, when suitably secured in position, an end of the rolled section, first'cut if necessary to result in the presentation of the end of a prospective shank portion 2', is centrally drilled at l by a conventional drill bit 8 (Fig. 11)

and, either simultaneously, or in a separate step which might be performed either prior to or subsequent to the drilling if desired, the peripheries of the outer and rear sides of the wings are turned and the prospective shank portion 2' is reduced to the desired diameter for threading. A groove 23 to provide clearance for threading will also desirably be turned in any suitable manner at the end of the first prospective shank portion, as is illustrated in Fig. 13. Also beveling of the forward end of the first lobed portion may be per-- formed as shown at l3 in Fig. 13. As shownin Fig. 12, the shank 2' is threaded by any suitable means, as for example by a. die 25. The bit is then cut off, as shown in Fig. 13, by a suitable cutting-oil tool l8; and if desired, concurrently, the provision of a bevel surface l3 can be formed on the blank next to be formed into a bit, and

the next clearance groove 23 be formed. It will while these still remain on the bar, thereby to in Fig. 13, they may be milled in a conventional milling machine to form a central recess l9 into which the bore I opens at the forward face of the bit. These blanks are further milled transversely to provide diametric cutting edges 20' and arcuate peripheral chopping edges 2|. This method differs somewhat in the sequence of operations from the first method disclosed, and specifically, in the steps performed on the connecting portions of the bits, primarily in that an external instead of an internal threading is employed. It will be evident that some of the operations illustrated as concurrently performed may be performed in sequence, as is the case with the first method described. Again, after all of the machining operations are completed the bit will be hardened, drawn and quenched or otherwise heat treated as may be necessary.

As a result of this, invention, an improved general method and improved specific methods of forming articles of manufacture, such as rock drill bits, are provided, whereby the majority of the bit forming operations are performed automatically by an automatic machine, thereby materially reducing handling costs and resulting in more perfect bits. It will further be evident that by forming the bit blanks from a section of bar stock suitably rolled into proper shape, and by per-.

forming the blank-forming operations wholly automatically, the drill bits are not only improved, but are also made of substantially uniform quality. Other advantages of the improved method of forming rock drill bits will be clearly apparent to those skilled in the art.

While the bit shank is illustrated as externally threaded andthe bit skirt as internally threaded, it will be evident that other forms adapted to locking cooperation with a drill steel may be ap-.

plied to the bits without departing from the broad scope of my invention.

This application is a continuation-in-part of ,my application Serial No. 416,110, filed October 22, 1941 now abandoned.

While there are in this application specifically described two forms which the invention may assume in practice, it will be understood that these forms of the same are shown for purposes of illustration, and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a method of forming detachable rock drill bits, the steps including preforming an elongated section of metal stock by causing the heated metal to flow into the desired shape to provide at uniform intervals a series of lobe-like enlargements which ultimately become bit wings, and, intermediate said enlargements, reduced portions which ultimately become means for effecting bit attachment to drill steels, the combined lengths of each enlargement and associated reduced portion bein such as to permit the formation of but a single bit by the making of a bit body at least mainly from said enlargement and a bit attachment portion at least mainly from said reduced portion, and said enlargements all facing in the same direction, machining the enlargement and reduced portion of an end por- 1 tion of the preferred stock section respectively bar stock to provide at uniform intervals a series of lobelike enlargements which ultimately become bit wings and to provide intermediate said enlargements reduced portions which ultimately become bit skirts, said enlargements having relatively steep end surfaces all facing in the same direction and further having more gradually tapering surfaces merging into reduced portions and all facing in the other direction, providing the reduced portion at the end of the bar stock towards which said more gradually taperin surfaces face with threads, machining the periphery of the immediately adjacent enlargement, and cutting off the partially machined bit by severing-the next adjacent reduced portion just beyond said immediately adjacent enlargement.

3. A method of forming a detachable rock drill bit, including the steps of rolling a section of bar stock to provide at uniform intervals a series of lobelike enlargements which ultimately become bit wings and to provide intermediate said enlargements reduced portions which ultimately become bit skirts, said enlargements having relatively steep end surfaces all facing in the same direction and further having more gradually tapering surfaces merging into reduced portions and all facing in the other direction, drilling and tapping the reduced portion at the end of the bar stock towards which said more gradually tapering surfaces face and machining the periphery of the immediately adjacent enlargement, cutting off the partially machined bit by severing the next adjacent reduced portion just beyond said immediately adjacent enlargement, and thereafter machining by a milling operation the cut oil", partially formed bit to provide a but a single bit, and reduced portions, which ultimately become the skirts of a single bit, said enlargements all facing in one direction and tapering, in the opposite direction, towards their associated reduced portions, workin the end reduced portion to form thereon means for securing it to a drill steel and shaping the immediately adjacent enlargement to form bit wings, cutting off the partially formed bit by severing the next adjacent reduced portion close to the enlargement to be cut off, and formingcutting edges on the severed enlargement in positions at least close to the surface left thereon by the severing operation.

5. A method of forming a detachable rock drill bit which includes the steps of rollin a section of bar stock into a shape providing a series of alternating enlargements and reduced portions, said enlargements ultimately becoming the cutting portions of drill bits and said reduced portions ultimately becoming bit skirts and said enlargements each comprising ends of relatively large radial dimension and opposite ends taper aneaesa ing from :iaid first mentioned ends and mer ing into adjacent reduced portions, and said enlargements all having their ends of relatively large radial dimension provided with surfaces facing in the same direction lengthwise of said bar stock; providing, at the end of the bar stock away from which said surfaces face and at the extremity of a reduced portion remote from the tapering end of an enlargement which merges into said reduced portion, a smooth surface suited for drilling'axially of the bar stock; drilling and tapping said reduced portion at said end of the bar stock; severing the drilled and tapped portion and the immediately adjacent enlargement from the bar stock by cutting the stock at the next adjacent reduced portion close to the eniargement which is to be cut ofl; and finally milling the severed portion into the shape of a completed drill bit.

6. A method of formin detachable rock drill bits, including the steps of producing a section of bar stock in a shape providing a series of alternating enlargements and reduced portions with the end of the bar stock to be worked terminating in a reduced portion, said enlargements ultimately becoming the cutting portions of the drill bits and said reduced portions ultimately becoming bit skirts, and said enlargements all facing the same direction away from said end to be worked. drilling and tapping each reduced portion while it remains unsevered from the bar stock at the end of the latter, severing the drilled and tapped portion and the immediately adjacent enlargement from the stock by cutting the stock at the adjacent end of the next adjacent reduced portion close to and just at the other side of said enlargement from the drilled and tapped extremity of the bar stock, and finally milling the severed portion into the shape of a completed drill bit.

7. A method of forming detachable rock drill bits, including the steps of rolling a section'of bar stock into ashape providing a series of alter-' nating enlargements and reduced portions with the end of the bar stock to be worked terminating in a reduced portion, said enlargements ulti-' mately becoming the cutting portions of the drill bits and said reduced portions ultimately becoming bitskirts, and said enlargements all facing the same direction away from said end to be worked, drilling and tappingeach reduced portion while itremains unsevered from the bar stock at the end of the latter-and shaping the periphery of each immediately adjacent enlargement also before severance, severing the drilled and tapped portion and the immediately adjacent enlargement from the stock by cutting the stock at the adjacent end of the next adjacent reduced portion close to and just at the other 7 side of said enlargement from the drilled and tapped extremity of the bar stock, and finally milling the enlargement of the severed portion to provide cutting edges substantially at the severed face.

8. A method of forming detachable rock drill bits, including the steps of producing a section of bar stock in a shape providing a series of alternating enlargements and reduced portions with the end of the bar stock to be worked terminating in a reduced portion, .said enlargements ultimately becoming the cutting portions of drill bits and said reduced 'portions ultimately becoming the connecting portions of drill bits, and said enlargements all facing the same direction away from said end to be worked, drilling each reduced portion while it remains unsevered from the bar stock at the end of the latter and forming the bar end so produced to cooperate with holding means on the end of a drill steel, turning the periphery of the enlargement adjacent each reduced portion also while the latter remains integral with the bar stock at the end of the latter, then severing the drilled and formed reduced portion and the immediately adjacent enlargement from the stock while leaving the next adjacent reduced portion substantially wholly upon the bar stock, and finally milling the severed portion into the shape of a completed drill bit. I

9. A method of forming detachable rock drill bits, including the steps of producing a section of bar stock in a shape providing a series of alternating enlargements and reduced portions with the end of the bar stock to be worked terminating in a reduced portion, said enlargements ultimately becoming the cutting portions of the drill bits and said reduced portions ultimately becoming bit skirts, and said enlargements all facing the same direction away from said end to be worked, drilling and tapping each reduced portion and turning the periphery of each immediately adjacent enlargement while they remain unsevered from the bar stock at the end of the latter, severing the drilled and tapped reduced portion and the turned, immediately adjacent enlargement from the stock while leaving the next adjacent reduced portion substantially wholly upon the bar stock, and finally milling the enlargement of the severed portion to provide cutting edges substantially at the severed face.

10. A method of forming detachable rock drill hits, including the steps of preforming an elongated section of metal stock by causing the heated metal thereof to flow into a bar providing a series of alternating enlargements and reduced portions with the end of the bar to be worked terminating in a reduced portion, 'said enlargements ultimately becoming cutting portions 01' single drill bits and said reduced portions ultimately becoming connecting portions of single bits and said enlargements each including portions of relatively large radial dimension all facing in the same. direction away from said end of the bar and adapted to have cutting edges formed at their ends facing in said direction, partially forming a bit by machining operations on said end portion of said bar, severing the partially machined bit from the bar by cutting the bar at the next adjacent reduced portion close to the enlargement which forms a part of the partially machined bit, and forming a cutting face upon the enlargement of the severed,

partially machined bit.

11. A method of forming detachable rock drill bits, including the steps of preforming an elongated section of metal stock by causing the heated metal to flow into a bar made up of series of alternate lobed portions and substantially cylindrical portions, said lobed portions ultimately becoming cutting portions of single drill bits and said cylindrical portions ultimately becoming connecting portions of single bits, and said lobed portions each including portions of relatively large radial dimension all facing in the same direction away from one end of the bar and adapted to have cutting edges formed at their ends facing in said direction, partially forming a bit by machining operations on the cylindrical portion at said end of said bar, severing the partially machined bit from the bar by cutting the bar at the next adjacent substantially cylindrical portion close to the lobed portion which forms a part of the partially machined bit, and forming a cutting face upon the lobed portion of the severed, partially machined bit.

12. A method of forming a detachable rock drill bit, including the steps of rolling a section of bar stock to provide at uniform intervals a series of lobellke enlargements which ultimately become bit wings and-to provide intermediate said enlargements reduced portions which ultimately become bit shanks, said enlargements having relatively steep end surfaces all facing in the same direction and further having more gradually tapering surfaces merging into reduced portions and all facing in the other direction, drilling and threading the reduced portion at the end of the bar stock towards which said more gradually tapering surfaces face, machining the periphery of the immediately adjacent enlargement, and cutting of! the partially machined bit by severing the next adjacent reduced portion just beyond said immediately adjacent enlargement.

13. A method of forming a detachable rock drill bit, including the steps of rolling a section of bar stock. to provide at uniform intervals a series of lobelike enlargements which ultimately become bit wings and to provide intermediate'said enlargements reduced portions which ultimately become bit shanks, said enlargements having relatively steep and surfaces all facing in the same direction and further having more gradually tapering surfaces merging into reduced portions and all facing in the other direction, drilling and externally threading the reduced portion at the end of the bar stools towards which said more gradually tapering surfaces face and machinin the periphery of the immediately adjacent enlargement, cutting ofi the partially machined bit by severing the next adjacent reduced portion just beyond said immediately adjacent enlargement, and thereafter machining by a milling operation the cut-off, partially formed bit to provide a cutting face.

1 A method of forming a detachable rock drill bit which includes the steps of rolling a section of bar stock to provide at uniform intervals a series of lobelike enlargements which ultimately become bit wings and to provide intermediate said enlargements reduced portions which ultimately become bit connecting means, said emlargements having relatively steep end surfaces all facing in one direction and further having more gradually tapering surfaces merging into reduced portions and all facing in the other direction, turning the peripheries of the enlargement and of the reduced portion at the end of the bar stock towards which the more gradually tapering surfaces face, drilling and threading said reduced portion, cutting on said enlargement and reduced portion from the bar stock at a point just beyond said enlargement, and forming edges on the face of said severed enlargement.

15. A method of forming detachable rock drill bits which includes the steps of rolling a section of bar stock to provide at uniform intervals 9. series of lobelike enlargements which ultimately become bit wings and to provide intermediate said enlargements reduced portions which ultimately become bit connecting means, said enlargements of a length to form the wings of but one bit, turning the periphery of, drilling axially, and

threading the reduced portion of one unit conof bar stock to provide at uniform intervals a series of lobelike enlargements which ultimately become bit wings and to provide intermediate said enlargements reduced portions which ultimately become bit connecting means, said enlargements of a length to form the wings of butone bit, turning the periphery of, drilling axially, and threading the reduced portion of one unit consisting of a lobelike enlargement and an adjacent reduced portion, cutting ed that unit, and during such cutting off operation, performing at least one operation on the unit next tobe processed, at a point spaced from the end of the latter.

17. In a method of forming detachable rock drill bits, the steps including producing a section of bar stock in a shape providing a series of alter:- nate enlargements and reduced portions with the end of the bar stock to be worked terminating in a reduced portion, said enlargements ultimately becoming the cutting portions of the drlli bits and said reduced portions ultimately becom ing means for eflecting bit attachment to drill steels, the combined lengths of each reduced por-- tion and associated enlargement being such as to permit the formation of but a single bit by the making of a bit body at least mainly from said enlargement and a bit attachment portion at least mainly from said reduced portion, machining the enlargement and reduced portion at said end of the bar stock respectively partially to form the drilling portion of a bit and to form a bit attachment portion, cutting of! the partially machined end portion by severing the next adjacent reduced portion close to the enlargement that is to be cut off, and forming a cutting face upon the severed enlargement.

JOHN C. CURTIS.

REFERENCES CITED The following references are of record in the flle of this patent:

Slovak June 5. 1945 Certificate of Correction Patent No. 2,463,953 March 8, 1949 JOHN C. CURTIS It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 28, before the Word for insert except; column 6, line 1, for preferred read preformed;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case In the Patent Office.

Signed and sealed this 27th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'asioner of Patents. 

